Pneumatic jack



Oct. 21 1924. 1,512,837

J. c. EVENDEN PNEUMATIC JACK Filed A112. 9, 192-2 2,1 13. [/Zi/Zfdf" 15 A6216. Er 0" Patent Oct. 21, 1924.

STATES PATENT OFFICE.

INEUMATIC JACK.

Appflloation filed August 9, 1922. Serial No. 580,739.

. To all whom tit may 00mm.-

Be it known that I, JAMES CHARLES EVENDEN, a subject of the King of Great Britain and Ireland, residing in Brooklyn, Wellington, New Zealand, have'invented a new and useful Improvement in Pneumatic Jacks; and'I do hereby declare the following to be a full, clear, and exact description of the same.

This invention relates to pneumatic lifting jacks, and the chief object of the invention is to provide a jack for raising motor cars when it is desired to remove a wheel or tyre, and in which an ordinary pneumatic tyrle pump may be employed to operate the ac a J Accordin to my invention the jack consists of a cy inder containing a plunger and a plunger rod having a head for engaging beneath the load, while means are provided upon the cylinder into which means depending from the head of the jack engage as the head is raised, while means are provided whereby the depending means may be brought out of engagement with the means upon the cylinder when it is desired to lower the load.

The invention will be illustrated in the accompanying drawings, wherein Figure 1, is a sectional elevation of a jack.

Figure 2, is a cross sectional plan on line A-A, Figure 1.

Figure 3, is a plan.

Figure 4, is a plan with a portion removed.

Figure 5, and

Figure 6, are enlarged views of details.

Referring to the drawings, the jack consists of a cylinder 1, containing a plunger 2 fixed upon the bottom end of a plunger rod 3 having a head 4: upon its top end for engagin beneath the load. The lower end of the cy inder 1 is threaded into a base 5 and made air tight therein by red lead or the like. The upper end of the cylinder is closed by a cap or cover 6 through which the plunger rod 3 passes and which is threaded upon theupper end of the cylinder, while a thick leather washer 7 having a hole 8 to fit the plunger rod 3, is held between the u er end of the cylinder 1 and the cap 6. The washer is oiled in order to provide a good joint between the washer 7 and the lunger rod 3.

The p unger 2 is formed of a metal ring 9 threaded upon a reduced end of the plunger rod, a bucket leather -10 being then placed over the reduced end, while a ring 11 threaded on the reduced end and retains the This valve may be of the usual pneumatic tyre type, but is provided at its inner end with a ball valve 15 under pressure of a spring 16 (see Figure 5) in order to rovide an additional safeguard against the leakage of air from the cylinder. The spring 16 is in compression between the ball 15 and a pipe 13 screwed into the valve 12 as shown. A relief pipe 17 threaded into the base 5 is controlled by a tap 18 threaded into the outer end of such pipe and controlling an air passage 19. The tap 18 is prevented from being completely removed by a pin 20 Working in a groove 21 in the tap. The inner end of the tap is conically pointed and enters a conical recess at the entrance of the passage 19, so that when the tap is screwed up air cannot leak out of the passage. As the tap is unscrewed air from the passage 19 is allowed to escape through an orifice 22.

Racks 24 are fixed upon each side of the cylinder 1 while arms 25 are pivoted on pins 26 in the head 1. These arms are gulded through slots 27 in the cap 6. The lower end of the arms form pawls 31 which engage with the teeth of the rack and as the plunger rises the pawls may fall by gravity into engageme'nt with the teeth of the rack, but referably springs 32 are employed which springs normally tend to retain the pawls into engagement with the teeth. Upon the cap 6 a pawl controlling plate 28 is pivoted upon pins 29 projecting from the cap and passing through arcuate slots 30 in the plate 28 in order to allow the plate to have a limited amount of circular movement. The arms 25 'bear against cam faces 33 on the plate 28 and the faces 33 are arranged so that when the plate is rotated to the position shown in Figure 4, the arms will be carried out to the position shown in dotted lines in Figure 1, with the pawls 31 clear of the teeth of the racks.

In operation the jack is placed in position beneath the load and air pumped into the cylinder 1 'by means of an ordinary pneumatic tyre pump which is fitted upon the valve 12. As the plunger rises carrying the load upwards the pawls 31 will ride over the teeth of the racks 24 and will fall into on agement with the teeth, so that immediate y umping ceases and the load falls throug, unavoidable leakage of air from the cylinder, the arms 25 will sup ort the load. When it is desired to lower t e load, air would be pumped into the cylinder in order to relieve the pressure of the load from the racks, and the pawl controllin plate 28 is then rotated by means of a han e 34 and the arms thrown outwardly and-the pawls clear of the teeth of the racks. The tap. 18 is now rotated and the air allowed to escape along the passage 19 to the orifices 22 and the. speed at WhlCh the load is lowered may be easily controlled by the tap.

What I claim is v 1. In a pneumatic jack having a plunge working in a c linder and a plunger rod having a head or engaging the load, rack members and pawl members, certain of said members being fixed to the cylinder and the other being movably connected to said head, whereby the teeth of said members will move relatively to one another as the head moves awa' from the cylinder, resilient means for forcln the teeth of certain of said members tower the teeth of the other members for locking the plunger rod against reverse movement as the head moves away from the cylinder, and a cam plate pivoted on said cylinder and engaging the movably mounted members to permit the teeth of the members to be separated when it is desired to move the head toward the cylinder.

2. In a pneumatic jack having a plunger working in a cylinder and a lun r rod having a head for en agin the ca a rack member and a paw mem r, one of said members bein connected to the cylinder and the otherieing connected to the head, both of said members being provided with inter-engaging teeth and one of the members being movably mounted so that the teeth of the members] may be disengaged when desired resilient means engaging one of the members for holding the teeth in enga ement when the head is moved away from t e cylinder, and a cam plate pivotally mounted on the cylinder and enga 'ng the movably mounted member, where y the movably mounted member ma be swung away from the other member w en the cam is turned and disengage said teeth.

3. In a pneumatic jack having a plunger working in a cylinder and a plunger rod carrying a head for enga ing beneath the load, vertical racks upon t e exterior of the cylinder, pawls pendant from the said head and adapted to rise over and engage the teeth of the said racks as the said plunger and head rise, a cam plate pivoted on the upper end of said cylinder, cam surfaces on said cam plate engagin with said pawls where as the said late 1s rotated said cam faces will throw t e said awls in an outwarddirection, substantia ly as described.

In testimony whereof, I have signed my name to this specification in the presence of two subscribing witnesses.

JAMES CHARLES EVENDEN. Witnesses:

Srnm H. Hrecs,

E. P. ODommnn. 

